展开树状视图中的特定项目

Question

How can I expand an item existing in a TreeView using code behind? For example, when I click in my menu I can expand the specific item in my TreeView .

private void MenuItem_Click(object sender, RoutedEventArgs e)
    {
        // expand the 3rd item in my treeview
    }

code in XAML :

<TreeView Height="525" HorizontalAlignment="Left" Margin="2,47,0,0" Name="treeView1" VerticalAlignment="Top" Width="168" FontFamily="Times New Roman" FontSize="12">
        <TreeViewItem Header="PL3 Line 1" IsExpanded="False">
            <TreeViewItem Selected="TreeViewItem_Selected">
                <TreeViewItem.Header>
                    <StackPanel Orientation="Horizontal">
                        <Image Source="/MonitoringSystemOfficeArea;component/Images/Computer.png" Height="22" Width="26"></Image>
                        <Label Content="Live Update" Width="70"></Label>
                    </StackPanel>
                </TreeViewItem.Header>
            </TreeViewItem>
            <TreeViewItem Selected="TreeViewItem_Selected_1">
                <TreeViewItem.Header>
                    <StackPanel Orientation="Horizontal">
                        <Image Source="/MonitoringSystemOfficeArea;component/Images/Calender.png" Height="24" Width="27"></Image>
                        <Label Content="Archives" Width="70"></Label>
                    </StackPanel>
                </TreeViewItem.Header>
            </TreeViewItem>
            <TreeViewItem Selected="TreeViewItem_Selected_100">
                <TreeViewItem.Header>
                    <StackPanel Orientation="Horizontal">
                        <Image Source="/MonitoringSystemOfficeArea;component/Images/Aha-Soft-Large-Calendar-Calendar.ico" Height="24" Width="27"></Image>
                        <Label Content="Archives / days" Width="88"></Label>
                    </StackPanel>
                </TreeViewItem.Header>
            </TreeViewItem>
        </TreeViewItem>
        <TreeViewItem Header="PL7 Line 2" IsExpanded="False">

...... and so on

Answer 1

You can use ExpandSubtree method ( msdn ):

TreeViewItem.ExpandSubtree Method

Expands the TreeViewItem control and all its child TreeViewItem elements.

private void MenuItem_Click(object sender, RoutedEventArgs e)
{
    // expand the 3rd item and all its child in treeview      
    TreeViewItem tvi = treeView1.Items[2] as TreeViewItem;
    if (tvi != null)
    {
        tvi.ExpandSubtree();
    }
}

If you want to expand only main item you should use IsExpanded property ( msdn ).

private void MenuItem_Click(object sender, RoutedEventArgs e)
{
    // expand the 3rd item in treeview      
    TreeViewItem tvi = treeView1.Items[2] as TreeViewItem;
    if (tvi != null)
    {
        tvi.IsExpanded = true;
    }
}

If you want to collapse the item set IsExpanded to false:

private void MenuItem_Click(object sender, RoutedEventArgs e)
{
    // collapse the 3rd item in treeview      
    TreeViewItem tvi = treeView1.Items[2] as TreeViewItem;
    if (tvi != null)
    {
        tvi.IsExpanded = false;
    }
}